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Item Comparative Studies on Crystalline and Amorphous Vinylidene Fluoride Based Fibrous Polymer Electrolytes for Sodium-Ion Batteries(Springer Singapore, 2020) Janakiraman, S.; Khalifa, M.; Biswal, R.; Ghosh, S.; Anandhan, S.; Adyam, A.In the present work, electrospun poly (vinylidene fluoride) (PVDF) and poly (vinylidene fluoride-co hexafluropropylene) (P(VdF-co-HFP)) fibrous membranes have been compared. Porous homo and copolymer fiber-based membranes with an interconnected structure, high porosity, large electrolyte uptake were prepared by an electrospinning route. The effect of crystallinity in terms of X-ray diffraction (XRD) was investigated for the fibrous polymer membranes (FPMs). The surface morphology of the FPMs is evaluated by field emission scanning electronmicroscopy (FESEM). The FPMswere soaked in 1MNaClO4-ethylene carbonate (EC)/diethyl carbonate (DEC) (1:1, vol%) solution to form fibrous polymer electrolytes (FPEs). The ionic conductivity of copolymer showed 1.126 mS cm−1 under ambient temperature (at 28 °C) higher than the homopolymer (0.79 mS cm−1) because of HFP unit. The electrochemical stability window of the copolymer membrane also enhanced and stable up to 4.9 V versus Na+/Na suitable for high voltage sodium rechargeable batteries. When tested with Na066Fe0.5Mn05O2 as cathode and Na metal as an anode, the cycle performance significantly improved for the copolymer. © Springer Nature Singapore Pte Ltd. 2021.Item Polymer Electrolytes and Separators for Magnesium-Ion Batteries(CRC Press, 2024) Singh, R.; Khalifa, M.; Janakiraman, S.; Adyam, V.; Anandhan, S.; Biswas, K.Magnesium (Mg)-ion-based rechargeable batteries are attractive because magnesium is bivalent, abundant, non-toxic, and inexpensive. In the development of Mg-ion batteries (MIBs) with high energy densities, their ionic conductivity and safety have become important features. The most commonly used cathodes are Mo6S8, MoO3, V2O5, MnO2, and TiO2, but they are limited due to low voltages (<2.0 V) and low specific capacities. Therefore, electrolytes are needed to improve the voltage stability and ease of synthesis. In this chapter, polymer electrolytes and separators in MIBs with liquid or gel electrolytes are briefly outlined. Polymer electrolytes are classified into two categories, namely solid polymer electrolytes and gel polymer electrolytes (GPEs). Solid polymer electrolytes have several advantages such as high safety, lightweight, and favorable mechanical properties, but their weakness is their relatively lower ionic conductivity. To overcome these issues, GPE, which is a combination of liquid electrolyte and a polymer matrix, is explored. Poly(vinylidene fluoride)-based gel electrolytes showed a high ionic conductivity of the order of 10−3 S cm−1 at room temperature. In GPEs, an electrolyte is used as an ion transport medium between the electrodes, whereas a polymer membrane acts as a separator, thereby eliminating the physical contact between the electrodes. © 2025 selection and editorial matter, Prasanth Raghavan, Akhila Das, and Jabeen Fatima M. J.Item Surface modification of steels using friction stir surfacing(Trans Tech Publications Ltd ttp@transtec.ch, 2012) Janakiraman, S.; Reddy, J.; Kailas, S.V.; Bhat, K.Friction stir surfacing is done to deposit commercial pure Al on medium carbon steel under open atmosphere conditions. Roughness of the substrate, normal load and tool rotation are the variables. Deposition is analysed with respect to continuity, width, composition and phase parameters. Good deposition is observed under a limited set of load and rotation speed. The deposit contains a mixture of steel and aluminium particles. © (2012) Trans Tech Publications.Item On line monitoring of quality of friction surfacing(Trans Tech Publications, 2014) Janakiraman, S.; Bhat, K.U.Quality of deposition during friction surfacing depends on a number of parameters. With instrumentation many of these parameters can be observed in real time. Monitoring of these parameters allows one to incorporate necessary corrections, whenever, that parameters goes out of the safe domain. Present investigation aims at the potential of monitoring some of these parameters online and the quality of the deposition. It is observed that spindle speed and torque are not effective parameters whereas monitoring material consumption or height of the consumable friction tool is very much useful in monitoring the quality of the deposition. © (2014) Trans Tech Publications, Switzerland.Item Formation of composite surface during friction surfacing of steel with aluminium(2012) Janakiraman, S.; Bhat, K.U.Commercial pure aluminium was deposited on medium carbon steel using friction surfacing route. An aluminium rod was used as the consumable tool. Normal load and tool rotation speed were the variables. Under certain combinations of load and speed the deposition was continuous and uniform. The deposit consisted of Al embedded with fine particles of iron. The interface between substrate material and deposited material was smooth and relatively small. A mechanism is discussed for formation of a composite surface on the steel substrate. © 2012 S. Janakiraman and K. Udaya Bhat.Item Electroactive poly(vinylidene fluoride) fluoride separator for sodium ion battery with high coulombic efficiency(Elsevier B.V., 2016) Janakiraman, S.; Surendran, A.; Ghosh, S.; Anandhan, S.; Adyam, A.Electroactive separators are recent interest in self-charging rechargeable batteries. In this study, electrospun polyvinylidene fluoride (PVDF) is characterized as an electroactive separator for Na-ion batteries. The intrinsic ?-phase with high porosity of the separator is confirmed from X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FESEM) and Atomic Force Microscopy (AFM) studies. The electroactive separator is immersed in 1M NaClO4-ethylene carbonate (EC)/diethyl carbonate (DEC) (1:1 by weight) solution. The physicochemical characteristics of electroactive separator electrolyte (EaSE) were investigated using sodium ion conductivity, ion transference number and contact angle measurements. Linear and cyclic voltammetry studies were also carried out for the electrolyte system to evaluate oxidation stability window. The inherent ?-phases of the separator as obtained by electrospinning has an ionic conductivity of ~ 7.38 × 10- 4 S cm- 1 under ambient condition. Sodium ion cell made from EaSE with Na0·66Fe0.5Mn0·5O2 as cathode and Na metal as anode has displayed a stable cycle performance with a coulombic efficiency of 92% after 90 cycles. © 2016 Published by Elsevier B.V.Item Electrochemical characterization of a polar ?-phase poly (vinylidene fluoride) gel electrolyte in sodium ion cell(Elsevier B.V., 2019) Janakiraman, S.; Surendran, A.; Biswal, R.; Ghosh, S.; Anandhan, S.; Adyam, A.A polar ?-phase poly (vinylidene fluoride) (PVDF) membrane is developed through the electrospinning method. PVDF gel electrolyte for sodium ion batteries was obtained by saturating the bare porous membrane in a liquid electrolyte, 1 M NaClO4 in EC: DEC (1:1 vol%). The physical and electrochemical characteristics of the polar ?-phase PVDF membrane are explored by X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Atomic force microscope (AFM), sodium ion conductivity, linear sweep voltammetry (LSV) and sodium ion transference number. The ionic conductivity of a polar ?-phase PVDF gel electrolyte exhibited 9.2 × 10?4 S cm?1, higher than the commercially used Celgard® 2400 membrane 0.36 × 10?4 S cm?1 at ambient temperature. The electrochemical expolarations of the sodium ion half-cell (Na2/3Fe1/2Mn1/2O2) as a cathode and sodium metal as a counter electrode) conducted from PVDF gel electrolyte are analysed by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). CV of the battery showed a pseudo capacitive nature. The equivalent circuit model of the sodium ion cell brought out the effect of dipole moments in the polymer chains on the battery performance. © 2018 Elsevier B.V.Item A new strategy of PVDF based Li-salt polymer electrolyte through electrospinning for lithium battery application(Institute of Physics Publishing helen.craven@iop.org, 2019) Janakiraman, S.; Surendran, A.; Ghosh, S.; Anandhan, S.; Adyam, A.Polyvinylidene fluoride (PVDF) ultrafine fibers with different proportions of lithium nitrate (LiNO3) were fabricated by an electrospinning device. The processing parameters are optimized to 19 wt% PVDF to get a bead free structure. Scanning electron microscope (SEM) and atomic force microscope (AFM) showed the uniform and interconnected porous structure. With the addition of 2 wt% LiNO3, the fiber diameter of the electrospun membrane decreased from 371 to 222 nm. Furthermore, the addition of LiNO3 into the nanofibrous membrane enhanced the ionic conductivity from 0.97 ×10-3 S cm-1 to 1.61 ×10-3 S cm-1 at room temperature after soaking with 1 M LiPF6 (lithium hexafluoro-phosphate) in ethylene carbonate (EC) and diethyl carbonate (DEC) in (1:1 wt%). Compared with the conventional Celgard and pristine PVDF membrane, the salt doped PVDF membranes showed higher electrochemical stability window and lower interfacial resistance. The electrospun membrane separators (ES) were assembled into Lithium cobalt oxide (LiCoO2) as cathode and lithium metal as an anode. The salt doped membrane showed superior discharge, C-rate and stable cycle performance than the commercial Celgard membrane. © 2018 IOP Publishing Ltd.Item Electrospun electroactive polyvinylidene fluoride-based fibrous polymer electrolyte for sodium ion batteries(Institute of Physics Publishing helen.craven@iop.org, 2019) Janakiraman, S.; Surendran, A.; Biswal, R.; Ghosh, S.; Anandhan, S.; Adyam, A.Electrospinning is an efficient technique to produce ultrafine electroactive mat, diameters ranging from few nanometers to micrometers to use as a separator in sodium ion battery. The polyvinylidene fluoride (PVDF) polymer solution was optimized to 19 wt%, applied voltage 25 kV and flow rate of 0.5 ml h-1 to get a bead free ultrafine electroactive structure. The electroactive ?-phase is confirmed by x-ray diffractometer (XRD). Ionic conductivities, electrolyte uptake, wettability, linear sweep voltammetry (LSV) and thermal stability of the electroactive fibrous polymer electrolyte (EFPE) were studied by soaking the separator with a liquid electrolyte of 1 M sodium hexafluorophosphate (NaPF6) dissolved in ethylene carbonate (EC)/propylene carbonate (PC) (1:1 vol%). The EFPE exhibits high ionic conductivity of 1.08 mS cm-1 and electrochemical stability window of 5.0 V versus Na/Na+ under ambient condition. The half-cell containing Na0.66Fe0.5Mn0.5O2 as cathode and EFPE as the separator cum electrolyte showed a stable cycling performance at a current rate of 0.1C. © 2019 IOP Publishing Ltd.Item PVDF/halloysite nanocomposite-based non-wovens as gel polymer electrolyte for high safety lithium ion battery(John Wiley and Sons Inc. cs-journals@wiley.com, 2019) Khalifa, M.; Janakiraman, S.; Ghosh, S.; Adyam, A.; Anandhan, S.Gel polymer electrolyte (GPE) based on electrospun poly(vinylidene fluoride) (PVDF)/halloysite nanotube (HNT) nanocomposite non-wovens was synthesized and its suitability as a separator in lithium-ion battery (LIB) was explored. In this study, HNT played a key role in reducing the average diameter of the electrospun fibers and uplifted the porosity of the non-wovens thereby improving their electrolyte uptake. Due to a reduction in crystallinity and increased % porosity of the PVDF/HNT non-wovens, the ionic conductivity (1.77 mScm?1) and ionic transport across the separator were improved. Moreover, this GPE separator exhibited high tensile and puncture strength with negligible thermal shrinkage and a higher melting temperature compared with a commercially available separator, which is vital from the safety perspective. The cycling performance of Li/GPE/LiCoO2 cell was evaluated and it exhibited a high capacity of 138.01 mAhg?1 with 97% coulombic efficiency for the initial cycle. The cell was stable and retained its high performance with little loss in capacity even after repeated charge–discharge cycles. Such a combination of high ionic conductivity, tensile strength with low thermal shrinkage is seen to be very rare in polymer-based separators. It is noteworthy that this novel GPE outperformed the commercial separator also in the cycle performance. POLYM. COMPOS., 40:2320–2334, 2019. © 2018 Society of Plastics Engineers. © 2018 Society of Plastics Engineers